SPR-8698 Support flash attrs and a ModelAndView return value.

Before this change, flash attributes could only be added if via
RedirectAttributes.addFlashAttribute(..) if the method returned
a view name or a View instance. With this change, the above is
supported with a ModelAndView return value as well.

org.springframework.web.servlet/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ModelAndViewMethodReturnValueHandler.java

@@ -21,6 +21,8 @@ import org.springframework.web.context.request.NativeWebRequest;
 import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
 import org.springframework.web.method.support.ModelAndViewContainer;
 import org.springframework.web.servlet.ModelAndView;
+import org.springframework.web.servlet.SmartView;
+import org.springframework.web.servlet.View;
 
 /**
  * Handles return values of type {@link ModelAndView} copying view and model 
@@ -48,17 +50,29 @@ public class ModelAndViewMethodReturnValueHandler implements HandlerMethodReturn
 								  MethodParameter returnType, 
 								  ModelAndViewContainer mavContainer, 
 								  NativeWebRequest webRequest) throws Exception {
-		if (returnValue != null) {
-			ModelAndView mav = (ModelAndView) returnValue;
-			mavContainer.setViewName(mav.getViewName());
-			if (!mav.isReference()) {
-				mavContainer.setView(mav.getView());
+		if (returnValue == null) {
+			mavContainer.setRequestHandled(true);
+			return;
+		}
+		
+		ModelAndView mav = (ModelAndView) returnValue;
+		if (mav.isReference()) {
+			String viewName = mav.getViewName();
+			mavContainer.setViewName(viewName);
+			if (viewName != null && viewName.startsWith("redirect:")) {
+				mavContainer.setRedirectModelScenario(true);
 			}
-			mavContainer.addAllAttributes(mav.getModel());
 		}
 		else {
-			mavContainer.setRequestHandled(true);
+			View view = mav.getView();
+			mavContainer.setView(view);
+			if (view instanceof SmartView) {
+				if (((SmartView) view).isRedirectView()) {
+					mavContainer.setRedirectModelScenario(true);
+				}
+			}
 		}
+		mavContainer.addAllAttributes(mav.getModel());
 	}
 
 }
\ No newline at end of file

org.springframework.web.servlet/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ModelAndViewMethodReturnValueHandlerTests.java

@@ -18,6 +18,8 @@ package org.springframework.web.servlet.mvc.method.annotation;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotSame;
+import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
 
 import java.lang.reflect.Method;
@@ -26,10 +28,11 @@ import org.junit.Before;
 import org.junit.Test;
 import org.springframework.core.MethodParameter;
 import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.ui.ModelMap;
 import org.springframework.web.context.request.ServletWebRequest;
 import org.springframework.web.method.support.ModelAndViewContainer;
 import org.springframework.web.servlet.ModelAndView;
-import org.springframework.web.servlet.mvc.method.annotation.ModelAndViewMethodReturnValueHandler;
+import org.springframework.web.servlet.mvc.support.RedirectAttributesModelMap;
 import org.springframework.web.servlet.view.RedirectView;
 
 /**
@@ -45,44 +48,90 @@ public class ModelAndViewMethodReturnValueHandlerTests {
 
 	private ServletWebRequest webRequest;
 
+	private MethodParameter returnParamModelAndView;
+
 	@Before
-	public void setUp() {
+	public void setUp() throws Exception {
 		this.handler = new ModelAndViewMethodReturnValueHandler();
 		this.mavContainer = new ModelAndViewContainer();
 		this.webRequest = new ServletWebRequest(new MockHttpServletRequest());
+		this.returnParamModelAndView = getReturnValueParam("modelAndView");
 	}
 	
 	@Test
 	public void supportsReturnType() throws Exception {
-		assertTrue(handler.supportsReturnType(getReturnValueParam("modelAndView")));
+		assertTrue(handler.supportsReturnType(returnParamModelAndView));
 		assertFalse(handler.supportsReturnType(getReturnValueParam("viewName")));
 	}
 
 	@Test
-	public void handleReturnValueViewName() throws Exception {
+	public void handleViewReference() throws Exception {
 		ModelAndView mav = new ModelAndView("viewName", "attrName", "attrValue");
-		handler.handleReturnValue(mav, getReturnValueParam("modelAndView"), mavContainer, webRequest);
+		handler.handleReturnValue(mav, returnParamModelAndView, mavContainer, webRequest);
 		
 		assertEquals("viewName", mavContainer.getView());
 		assertEquals("attrValue", mavContainer.getModel().get("attrName"));
 	}
 
 	@Test
-	public void handleReturnValueView() throws Exception {
+	public void handleViewInstance() throws Exception {
 		ModelAndView mav = new ModelAndView(new RedirectView(), "attrName", "attrValue");
-		handler.handleReturnValue(mav, getReturnValueParam("modelAndView"), mavContainer, webRequest);
+		handler.handleReturnValue(mav, returnParamModelAndView, mavContainer, webRequest);
 		
 		assertEquals(RedirectView.class, mavContainer.getView().getClass());
 		assertEquals("attrValue", mavContainer.getModel().get("attrName"));
 	}
 
 	@Test
-	public void handleReturnValueNull() throws Exception {
-		handler.handleReturnValue(null, getReturnValueParam("modelAndView"), mavContainer, webRequest);
+	public void handleNull() throws Exception {
+		handler.handleReturnValue(null, returnParamModelAndView, mavContainer, webRequest);
 		
 		assertTrue(mavContainer.isRequestHandled());
 	}
 
+	@Test
+	public void handleRedirectAttributesWithViewReference() throws Exception {
+		RedirectAttributesModelMap redirectAttributes  = new RedirectAttributesModelMap();
+		mavContainer.setRedirectModel(redirectAttributes);
+		
+		ModelAndView mav = new ModelAndView(new RedirectView(), "attrName", "attrValue");
+		handler.handleReturnValue(mav, returnParamModelAndView, mavContainer, webRequest);
+		
+		assertEquals(RedirectView.class, mavContainer.getView().getClass());
+		assertEquals("attrValue", mavContainer.getModel().get("attrName"));
+		assertSame("RedirectAttributes should be used if controller redirects", redirectAttributes,
+				mavContainer.getModel());
+	}
+
+	@Test
+	public void handleRedirectAttributesWithViewInstance() throws Exception {
+		RedirectAttributesModelMap redirectAttributes  = new RedirectAttributesModelMap();
+		mavContainer.setRedirectModel(redirectAttributes);
+		
+		ModelAndView mav = new ModelAndView("redirect:viewName", "attrName", "attrValue");
+		handler.handleReturnValue(mav, returnParamModelAndView, mavContainer, webRequest);
+		
+		ModelMap model = mavContainer.getModel();
+		assertEquals("redirect:viewName", mavContainer.getViewName());
+		assertEquals("attrValue", model.get("attrName"));
+		assertSame("RedirectAttributes should be used if controller redirects", redirectAttributes, model);
+	}
+	
+	@Test
+	public void handleRedirectAttributesWithoutRedirect() throws Exception {
+		RedirectAttributesModelMap redirectAttributes  = new RedirectAttributesModelMap();
+		mavContainer.setRedirectModel(redirectAttributes);
+		
+		ModelAndView mav = new ModelAndView();
+		handler.handleReturnValue(mav, returnParamModelAndView, mavContainer, webRequest);
+		
+		ModelMap model = mavContainer.getModel();
+		assertEquals(null, mavContainer.getView());
+		assertTrue(mavContainer.getModel().isEmpty());
+		assertNotSame("RedirectAttributes should not be used if controller doesn't redirect", redirectAttributes, model);
+	}
+
+
 	private MethodParameter getReturnValueParam(String methodName) throws Exception {
 		Method method = getClass().getDeclaredMethod(methodName);
 		return new MethodParameter(method, -1);